The proposed study is the continuation of the Early Growth and Development Study (EGDS), a prospective adoption design consisting 350 adoption triads (birth parents, adopted child, and adoptive parents). The overarching aim of this work is to study mechanisms of Genotype x Environment (GxE) interaction to identify environmental processes that prevent the expression of genetic risk and promote the expression of genetic resilience. We focus on mechanisms of GxE interaction along three developmental pathways: internalizing behavior, externalizing behavior, and social competence. We also explore hypotheses regarding the role of three early responding systems that are closely linked to these pathways: emergent literacy, HPA axis functioning, and executive functioning. The proposed data collection consists of multimethod, multiagent measures of genetic risk and protective factors, environmental processes, and children's behavioral and neuroregulatory development during the transition to primary school. Success or failure during this transition has long-term implications for children's mental health and drug use. Birth parent in-person assessments are proposed at child age 5, and adoptive family in-person assessments are proposed at ages 41/z, 6 (kindergarten), and 7 (first grade). The following aims are proposed: (1) To identify specific parenting processes that mediate the expression of genetic influences on children's internalizing behavior, externalizing behavior, and social competence (genotype-environment correlation);(2) to identify specific parenting processes and contextual factors that moderate genetic influences on internalizing behavior, externalizing behavior, and social competence (GxE interaction);(3) to identify mechanisms by which parenting and adoptive family contextual factors moderate genotype expression;and (4) to explore early responding systems that may moderate a child's effect on or sensitivity to the family environment. Public Health Relevance: Young children's externalizing and internalizing problems pose critical challenges for families and schools. Children who enter primary school with problems are more likely to struggle academically and to access mental health and social services as adolescents and adults. The proposed work would build an empirical foundation to help guide prevention programs administered in family settings.